Acoustic telephone



2 Sheets-Sheet 1.

W. HUBBARD. Acoustic Telephone.

Patented Feb. 22,1881.

N.FETFES PHOm-LITHQGRAPHER, WASNKHGTON. D Cv 2 Sheets-Sheet 2. W.HUBBARD.

Acoustic Telephone.

No. 237,979. Patented Feb. 22,1881.

UNITED STATES WILLIAM HUBBARD, OF ELGIN, ILLINOIS.

ACOUSTIC TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 237,979,

dated February 22, 1881.

Application filed January 3, 1880.

To all whom it may concern Be it known that I, WILLIAM HUBBARD, ofElgin, in the county of Kane and State of Illinois, have invented acertain new and useful Improvement in Acoustic Telephones and I dohereby declare the following to be a full, clear, and exact descriptionof the same, reference being had to the accompanying drawings, formingpart of this specification, in which Figure 1 represents a front viewwith the cap L in place; Fig. 2, a similar view with the cap L removed.Fig. 3 is a sectional view taken on the line 00 00,Fig. 1. Figs. 4, 5,and 6 are views showing the application of the invention to the purposesof a telephone-exchange. Fig. 7 illustrates the old mode of putting upacoustic-telephone wires, and Fig. 8 illustrates my improved mode.

Similar letters of reference in the several figures denote the sameparts.

This invention relates to that class of speaking-telephones in whichatmospheric soundvibrations are reproduced at a distance through themedium of diaphragms connected by wires or their equivalents; and itconsists in several improvements which tend to increase the e1"-fectiveness of this class of instruments and adapt them to the purposesof a telephone-exchange, all which I will now proceed to describe.

In the drawings, A indicates the back plate of the instrument, B thediaphragm, and O the front plate, the construction of the parts beingsuch as to form a chamber, D, behind the diaphragm, and a chamber, E, infront of it. The wire F, or its equivalent, is connected, in the usualmanner, to a button, G, at the center of the diaphragm.

I provide the back plate, A, with a central tubular extension, a, on itsside, which extension is intended to enter the opening in the wall orother support, and thereby center the instrument with such openin '1recommend that the extension be slightly tapered toward its outerextremity, and that it be provided with exterior screw-threads, by whichit can be screwed into and securely held in the opening provided, asaforesaid, for the passage of the wire. By this construction the wirewill be caused to extend centrally through the opening and through thetube a to the button G atthe middle of the diaphragm.

The plate A is cast or constructed in concavo-couvex form, with a smallcircumferential flange, a, through which screws are inserted, to connectit to the front plate and securethediaphragmin position. Bythismeans thechamber D is constructed in piano-convex form, which my experiments haveproved to be superior to the forms heretofore in use, in that it causesan increased force in the vibrations of the diaphragm, and thereby anincreased volume in sound. To prevent the ringing or echoing which isgenerally observed in this class of instruments, the chamber or chambersmay be lined with felt, paper, or other non-resonant substance.

The front plate, 0, is constructed with an external flange, 0, throughwhich to receive the screws which connect the front and back plates ofthe diaphragm together, and at the inner edge of such flange it extendslaterally nearly at right angles to the plane of the flange, thusforming an annular shoulder, c, from the edge of which it extends inwardand backward to the central opening, 0 The result of this constructionis a chamber, E, of plano-concave form, which I have found to be bestsuited to the purposes of the instrument, in that it gives a somewhatincreased force of vibration to the diaphragm, and at the same timeadapts the instrument to be spoken into and to be properly applied tothe ear.

The instrument, so far as above described, is applicable both to thesending and receiving of spoken messages or other sounds or signals.

Another part of my invention consists in adapting the class oftelephones to which this invention pertains to being operated inconnection with what is known as a telephoneexchange, whereby differentlines or instruments can be put into direct connection with each otherby means of a system of switches or interchangeable connections at anintermediate central office.

To explain the manner in which I accomplish this, let E, Fig. 4,represent an instrument which it is desired to put into communicationwith the distant instrument I through the medium of the telephoneexchange J,

wherein an is the receiving-instrument connected to the station E, and nis the receiving instrument connected to the station I. Normally the twolines m H and n I are disconnected, and this part of my inventionconsists in providing means whereby the received vibrations of thediaphragm of the instrument m may be transmitted to the diaphragm of theinstrument a, and therefrom to the final receiving-station I. Theconnection between the two instruments m n, for the purpose aforesaid,may be effected either by a direct wire extending from one diaphragm tothe other, or by a column of air confined in a tube extending from onediaphragm to the other, it only being necessary that the vibrations ofthe diaphragm m should be communicated to the diaphragm at, either ofthe above means satisfactorily answering the purpose and .in thisconnection I would state that I do not confine myself to the use of ametal wire specifically, as a string or other similar article might besubstituted nor do 1 limit myself to a column of atmospheric air, as acolumn of gas or any other fluid or liquid capable of transmittingsound-vibrations without interfering with the action of the diaphragmwould answer the same purpose.

The details of the connections of the telephone-exchange may be arrangedin various ways. With the wire or cord connection it is only necessaryto attach an eye, a, to the front side of the button G, or at the frontand center of the diaphragm of the receiving-instruments, as shown inFigs. 1, 2, 3, and then connect the eyes of the tworeceiving-instruments by means of a connecting-wire, K, to which asuitable tension is imparted by a spring, k, of any form andconstruction. With this arrangement the vibrations recorded at m will betransmitted through the wire or cord K to the diaphragm a, and thence tothe station I.

A single switch-board, as shown in Fig. 4, may be employed for thepurpose, or a double switch-board, as shown in Fig. 5. In the formercase the receiving-instruments are arranged side by side and thestraining-springs are arranged opposite to the board. In the latter casethe receiving-instruments are arranged opposite to each other, and thesprings preferably form a portion of the direct connection between them,as shown by the drawings. Any number of receiving-instruments may bethus arranged, and by means of suitable wires and springs any two of theinstruments may be connected together for the purpose of transmitting amessage. The call is made simply by tapping upon the sending-diaphragmwith a pencil or other light instrument, in response to which theattendant, having ascertained what station it is desired to communicatewith, hooks one end of a connecting-wire into the eye of the instrumentthrough which the call is received, and the other end through the eye ofthe instrument through which the communication is to be transmitted toits ultimate destination.

When the connection between the receivinginstrument is to be effected bya column of air or other similar fluid, the receiving-instruments areeach to be provided with a cap, L, which fits tightly over and aroundthe shoulder a, and is fastened thereto by a bayonet-joint or othersuitable fastening. This cap is provided with a conical mouth-piece, l,capable of being tightly closed by a cover, Z and it is further providedwith one or more projecting tubes, 0 0, the ends of which should becorrugated or roughened externally, or provided with screw-threads forthe attachment of a flexible tube. The inner ends of the tubes 0 0extend nearly to the central opening of the face-plate O. The tubes areinclined from each other for the purpose of bringing their inner endsnearer together and of leaving room between them for the conical openingthrough the cap. Preferably I arrange a pitch-pipe in one of the tubes 00, by which a distant station may be called or signaled. The mode offorming the connection at the telephone-exchange bymeans of these tubesis shown in Fig. 6, and the operation is as follows: The conicalopening! being normally uncovered, any signal may be readily heardthroughit. The attendant at the exchange, after ascertaining the stationwith which it is desired to connect, will then close said opening bymeans of the plate l, and will connect the tubes 0 0 of thereceiving-instrument on to the tubes 0 0 of the receiving-instrument aby means of two flexible or jointed and preferably elasticconnecting-tubes, p, as

shown in Fig. 6. The vibrations of the diaphragm in will then betransmitted through the contained columns of air in the tubularconnections to the diaphragm a, and thence to the ultimatereceiving-station.

I have found in practice that the tubular connections and the directmetallic connec tions are substantially practical equivalents of eachother in the operation of this class of telephones for the purposesreferred to. The tubular connection and also the wire connection arehere shown and described as extending from the-front side of onediaphragm to the front side of another; but there is believed to be noreason why a similar tubular connection between the rear side of the twoinstruments, or from the rear side of one to the rear side of another,would not answer the same purpose. The flexible tubes are of advantagefor other purposes than that of connecting the instruments at theexchange. They may be used as wellat the end of the line, and when thereused can be conducted from the instrument to any part of the room, andby means of them the telephone can be readily worked without thenecessity of going to the instrument itself either to call or carry onthe communication. Another great advantage derived from them is thesaving of at least four angles in a single wire running to places inopposite directions and communicating to the rooms on the lower floors.Heretofore such lines have been arran ged substantially as shown in Fig.7, necessitating the angles 1 2 3 4 in order to raise the body of thewire high out of the way between the buildings; but by means of thetubular connections at the end the wires can extend directly between theupper part of the buildings, as shown in Fig. 8, with the instrumentsarranged directly at their ends, and the speaking-tubes extending downfrom the instrument to the apartment or place most convenient foroperatiu g. In this case the central opening, I, of the cap L should beclosed.

The mouth-piece at the end of the flexible tube is funnel-shaped, havinga stem of the same size as the metallic tube, so that the rubber orflexible tube, when slipped off at the month-piece, will flt on or inthe tube of another attachment. Any other form of mouthpiece may besubstituted in place of the one shown, if desired.

I do not claim as my invention the tubular central stem or projection atthe rear side of the instrument, through which the wire is received andby which the instrument is centered and supported; nor do I claim thecombination, in an acoustic telephone, of a hollow sound-conveyerpassage or tube, or a flexible diaphragm adapted to transmit sound to orfrom the air or other fluid contained in the hollow conveyer; but

That I do claim as my invention, and desire to secure by Letters Patent,is-

1. In an acoustic telephone, a diaphragm provided with means for theattachment of wires to both its front and rear sides, whereby theinstrument is adapted to the purposes of an exchange, substantially asdescribed.

2. An acoustic-telephone instrument having a front plate, 0, with acentral opening and a raised rim or shoulder, 0, whereby the internalchamber, E, increases in size from the central opening toward theshoulder, substantially as described.

3 In an acoustic-telephone instrument, the combination of the backplate, the diaphragm, and the dishing front plate having the centralopening, of a removable cap to inclose and confine the air in front ofthe front plate, said cap having a tapering tubular opening at itscenter, and tubes which communicate with the diaphragm, substantially asdescribed.

4. The combination of the back plate, the diaphragm, the front plate,and the cap, said cap having a tapering central tubular opening, with aremovable plate for closing it.

IVILLIAM HUBBARD.

Witnesses:

F. A. EDWARDS, War. G. HUBBARD.

